1. Field of the Invention
The present invention relates to an ink for an ink-jet printer.
2. Description of the Prior Art
An ink-jet printing process has attracted intense interest recently for printing letters or symbols on the surface of mass-produced industrial products or packed boxes, etc.
The ink-jet printing process has heretofore been used in terminal printing of an electronic computer, etc., but the substrate has been paper. Therefore, water-soluble inks have been used in the process (U.S. Pat. No. 3,687,887).
According to the ink-jet printing method, an ink sent from a storage tank by the action of compressed air, etc. enters an ink-jet apparatus having an orifice of 20 to 150 .mu.m in diameter, where the ink is converted into a continuous flow of fine particles by the action of a vibrator operated magnetically or electrically. In the course from said jet apparatus to a printing substrate, the flow of fine particles is controlled by a video signal from an electronic character generator and an electrostatic deflection system and prints letters and symbols continuously on the printing substrate.
In the above-mentioned process, the ink particles must always be fine particles of a definite size and must respond sensitively to the action of said control system in order to keep the uniform density of the printed letters and symbols. Therefore, the properties such as viscosity, surface tension, specific gravity, electroconductivity, etc. of the ink are strictly controlled according to the shape, size and material of the nozzle and applied voltage, etc. Since prior art inks are printed on paper as described above, however, proposals on improvement in the process have exclusively been directed to water-soluble inks.